This invention is concerned with a machine for slip forming a concrete curb or curb and gutter and more particularly a curb with a base and a head which follow prescribed grades.
In my earlier U.S. Pat. No. 3,605,581 I show a machine which slip forms a curb and gutter with a fixed dimension between the gutter flag portion and the head or top of the curb. There are road designs in which this vertical curb dimension is not fixed, but varies from point to point along the road. Such curb and gutter cannot be slip formed with the machine shown in my patent.
Consider, for example, the problem of water drainage of a road over flat terrain. It is necessary that the gutter have a longitudinal pitch with a low point at each catch basin and a high point between adjacent catch basins. It is often desired, however, that the head or top of the curb be at a different grade, so as to match an existing sidewalk, for example. Such a design requires that the vertical dimension of the curb change from point to point along the road.
It is a principal feature of my invention that it provides a slip form machine which may be utilized in forming a curb or curb and gutter with a vertical dimension that varies. More specifically, it is a feature of the invention to provide a slip forming machine having moving carrier, a well for feeding concrete to a slip form, side walls for the slip form extending rearwardly from the well, a top wall between the side walls, means for moving the well and side walls vertically with respect to the carrier to establish the grade of the curb, and further means for moving the top wall vertically with respect to the side walls to establish the height of the curb.
Another feature is that the grade and height of the curb are established by a pair of grade lines and the slip forming machine includes a first line sensor mounted to the side walls to control movement of the side walls and a second line sensor mounted to the top wall to control movement of the top wall.
A further feature is that the rear wall of the well has an opening therein through which concrete passes into the slip form, the vertical dimension of the opening corresponding with the maximum height of the slip form top wall, and the top wall has a sealing plate which extends upwardly therefrom adjacent the rear wall of the well and blocks a portion of the opening when the top wall is at a position below its maximum height. More specifically, the sealing plate is held against the rear wall of the well by an adjustably mounted roller.
And another feature is that the top wall of the slip form is moved by a pair of hydraulic cylinders which are actuated to move in synchronism.